Part of semiconductor manufacturing includes the patterning of structures onto silicon wafers. The patterning is carried out by depositing a layer of photoresist material, then exposing a pattern onto the photoresist layer to selectively and lithographically alter the properties of the layer, then etching the exposed photoresist layer to selectively remove an underlying material in accordance with the exposed pattern, then removing the remaining photoresist.
Photoresist removal has been carried out by either batch wet-processing or single-wafer plasma dry processing. Batch wet-processing is commonly found in front-end on-line systems (FEOL) while single-wafer dry processing is commonly found in back-end on-line systems (BEOL). Initially, batch wet-stripping was used for resist removal, but processing costs were high and processing requirements were not satisfactorily met. Batch barrel plasma ashers were then tried, but wafer damage resulted. This led to the use of remote-plasma single-wafer dry systems. Companies providing the current dry stripping systems include Mattson, Novellus, Applied Materials and Axcelis. Patents describing some of these systems include U.S. Pat. Nos. 6,693,043, 6,638,875, 6,281,135, 6,630,406 and 6,834,656.
Wet strip systems today still provide low throughput, high chemical consumption cost and high equipment cost and require an excessive oxidizing environment. Dry plasma strip systems still suffer from plasma damage to the wafer.
Accordingly, there is a need for photoresist stripping that overcomes problems with the prior art.